avi to dvd format converter that allows letterboxing

I've tried a number of little programs such as ImTOO AVI to DVD converter, Avi2dvd and AVI DivX to DVD SVCd VCD Converter to convert a couple of personal .avi movie files to a format that'll work on dvd disks and play in a DVD player.

But when I go to play the disks on a normal television screen, I lose the sides of the image. A little research on the net tells me that I need a program that'll let me do something called letterboxing (which, some of the programs listed above claim to do, yet the problem remains.)

Is there a program out there that can encode the disk so that it'll display correctly on my tv and on my laptop, like the conventional dvd movies you purchase? I've noticed on these 'proper' dvd movies that the bars are smaller when I play them on my laptop (wider screen) than on my tv. I want this same effect.

Any help would be greatly appreciated, I’ve been searching for something that’ll do the job for months now.